The aetiology of colorectal cancer is heterogeneous, with environment or genetics playing varying key roles. About 80% of patients with colorectal cancer seem to have sporadic disease with no evidence of having inherited the disorder. In the remaining 20%, there seems to be a potentially definable genetic component.

Evidence for a genetic contribution to colorectal cancer includes increased risk of colorectal malignancy in persons with a family history and familial aggregation of colorectal cancer consistent with autosomal dominant inheritance. In the past decade, germline genetic mutations conferring high lifetime risk of colorectal cancer in carriers have been found, accounting for 5%–6% of all colorectal cancer cases.

Other gene mutations, some with lower lifetime risks, are continuing to be characterized. The translation into clinical practice of genetic discoveries related to hereditary colorectal cancer continues apace, primarily through improved risk assessment by genetic testing.

This review analyzes succinctly the most encountered colorectal cancer genetic syndromes of familial adenomatous polyposis and the current availability of genetic tests, describing indications for use of genetic tests in the hereditary colorectal cancer.